lib: add notmuch_threads_status()

While a number of errors can happen when iterating over threads
(DatabaseModifiedError, memory allocation errors, etc.), the API
currently cannot signal them to the caller, and either triggers an
internal error (aborting the caller) or returns NULL from
notmuch_threads_get() with no information on what actually went wrong.

Add a new public function notmuch_threads_status() - similar to
previously added notmuch_messages_status() - that allows propagating
those errors to the caller.

Use this to remove the INTERNAL_ERROR() in _notmuch_thread_create()
(triggered by T642).

Fixes: https://github.com/pazz/alot/issues/1460

Amended-By: db. Resolved whitespace disagreement between emacs and
uncrustify in favour of uncrustify.

1 files changed, 28 insertions, 9 deletions

diff --git a/lib/query.cc b/lib/query.cc
index 976fe76d..1761cdc9 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -61,6 +61,7 @@ struct _notmuch_threads {
     /* The set of matched docid's that have not been assigned to a
      * thread. Initially, this contains every docid in doc_ids. */
     notmuch_doc_id_set_t match_set;
+    notmuch_status_t status;
 };
 
 /* We need this in the message functions so forward declare. */
@@ -611,6 +612,7 @@ notmuch_query_search_threads (notmuch_query_t *query,
     threads = talloc (query, notmuch_threads_t);
     if (threads == NULL)
 	return NOTMUCH_STATUS_OUT_OF_MEMORY;
+    threads->status = NOTMUCH_STATUS_SUCCESS;
     threads->doc_ids = NULL;
     talloc_set_destructor (threads, _notmuch_threads_destructor);
 
@@ -651,10 +653,18 @@ notmuch_query_destroy (notmuch_query_t *query)
 notmuch_bool_t
 notmuch_threads_valid (notmuch_threads_t *threads)
 {
+    return notmuch_threads_status (threads) == NOTMUCH_STATUS_SUCCESS;
+}
+
+notmuch_status_t
+notmuch_threads_status (notmuch_threads_t *threads)
+{
     unsigned int doc_id;
 
     if (! threads)
-	return false;
+	return NOTMUCH_STATUS_ITERATOR_EXHAUSTED;
+    if (threads->status)
+	return threads->status;
 
     while (threads->doc_id_pos < threads->doc_ids->len) {
 	doc_id = g_array_index (threads->doc_ids, unsigned int,
@@ -665,26 +675,35 @@ notmuch_threads_valid (notmuch_threads_t *threads)
 	threads->doc_id_pos++;
     }
 
-    return threads->doc_id_pos < threads->doc_ids->len;
+    return (threads->doc_id_pos < threads->doc_ids->len) ?
+	   NOTMUCH_STATUS_SUCCESS : NOTMUCH_STATUS_ITERATOR_EXHAUSTED;
 }
 
 notmuch_thread_t *
 notmuch_threads_get (notmuch_threads_t *threads)
 {
+    notmuch_thread_t *thread;
     unsigned int doc_id;
+    notmuch_private_status_t status;
 
     if (! notmuch_threads_valid (threads))
 	return NULL;
 
     doc_id = g_array_index (threads->doc_ids, unsigned int,
 			    threads->doc_id_pos);
-    return _notmuch_thread_create (threads->query,
-				   threads->query->notmuch,
-				   doc_id,
-				   &threads->match_set,
-				   threads->query->exclude_terms,
-				   threads->query->omit_excluded,
-				   threads->query->sort);
+    status = _notmuch_thread_create (threads->query,
+				     threads->query->notmuch,
+				     doc_id,
+				     &threads->match_set,
+				     threads->query->exclude_terms,
+				     threads->query->omit_excluded,
+				     threads->query->sort,
+				     &thread);
+    if (status) {
+	threads->status = COERCE_STATUS (status, "error creating a thread");
+    }
+
+    return thread;
 }
 
 void